1. Field of the Invention
The present invention relates to a lead frame package structure. More particularly, the present invention relates to a lead frame package structure with high density of lead pins arrangement.
2. Description of the Prior Art
The lead frame package structure has been widely used in integrated circuit packages for a long time, resulting in its advantages of having a low cost and a high reliability. The lead frame package structure has accordingly gained a share of the market of low pin count packages.
Please refer to FIG. 1, FIG. 2, and FIG. 3. FIG. 1 is a schematic top view of a prior art lead frame package structure 10, FIG. 2 is a schematic side view of the prior art lead frame package structure 10 in FIG. 1, and FIG. 3 is a schematic top view of a prior art printed circuit board 30. As shown in FIG. 1 and FIG. 2, the prior art lead frame package structure 10 comprises a die 12, a plurality of lead pins 14, and a die positioned area 16. Each lead pin 14 comprises an inner terminal 22 and an outer terminal 24, and the die 12 comprises a plurality of bonding pads 18 electrically connected to the corresponding inner terminals 22 of the lead pins 14. In addition, there is a sealing glue 26 solidified for sealing the die 12 and the inner terminals 22 within the package structure. The sealing glue 26 is presumed to be transparent so that the inner structure of this prior art lead frame package structure 10 could be seen. As shown in FIG. 3, each inner terminal 22 of the lead pin 14 is electrically connected to a corresponding bonding pad 32 of the prior art printed circuit board 30. More particularly, the inner terminals 22 are arranged along a straight line in the prior art lead frame package structure 10. Similarly, the outer terminals 24 and the bonding pads 32 are arranged along a straight line, wherein there is a distance 24a between every two outer terminals 24 and a distance 32a between every two bonding pads 32.
However, in order to match up to the higher density integrated circuit product, the size of package structure should decrease without decreasing the quantity of lead pins, or the quantity of lead pins should increase without increasing the size of package structure. In other words, lead frame package structures with higher densities of lead pins arrangements should be developed. The lead pins arrangement of the prior art lead frame package structure 10 is limited in its ability to increase the density of lead pins. In the prior art, as the density of lead pins 14 increases, the distance 24a between every two lead pins 14 decreases, so that the probability of cross-talk, the probability of interference, and the difficulty of manufacturing the package structure increases. Theoretically, one lead pin 14 should only be electrically connected to one corresponding bonding pad 32. However, factors such as thermal expansion, flow of the solder, and misalignment may cause the lead pins 14 to couple with each other. As a result, the short lead pins 14 reduce the performance of products.
In the prior art lead frame package structure 10, the density of lead pins 14 should increase in order to decrease the size of lead frame package structure 10 or to increase the quantity of lead pins 14. Thus, the distance 24a between each terminal 22,24 decreases as the density of lead pins 14 increases. As a result, the probability of cross-talk, the probability of interference, and the difficulty of manufacturing the package structure increases. Briefly, the prior art lead pins arrangement is a poses a restriction on the development of higher density integrated circuit products.